1. Field of the Invention
The present invention relates to the separation of dienic and/or aromatic hydrocarbons present in hydrocarbon fractions employing sulfonamides; it relates more particularly to the use for this separation, using known techniques of liquid-liquid extraction and/or extractive distillation, of solvents selected from the group constituting the sulfonamides.
2. Description of the Prior Art
As used in the instant specification, the term sulfonamides embraces compounds having in their molecular structure the group &gt;N--SO.sub.2 --.
Numerous selective solvents for the recovery of hydrocarbons are described in the technical literature. With regard to the dienic hydrocarbons, one can particularly mention N-methylpyrrolidone, acetonitrile and dimethylformamide. One of the possible applications of these solvents is, for example, the selective extraction of isoprene from a cut of hydrocarbons in which the number of carbon atoms is equal to about 5 (this cut of hydrocarbons is commonly referred to as the "C.sub.5 fraction").
Among the known selective solvents for the extraction of aromatic hydrocarbons, one can mention sulfolane, N-methyl-pyrrolidone in aqueous solution, derivatives of morpholine such as N-formylmorpholine or dimethylsulfoxide.
It is also known to use certain saturated aliphatic sulfonamides to separate dienic and/or aromatic hydrocarbons.
In French patent application No. 78 29828 of Oct. 19, 1978, of which the applicants are assignees, there are described for such a use sulfonamides of the general formula: ##STR2## wherein R' and R" are saturated alkyl groups possessing from 1 to 4 carbon atoms.
Sulfonamides of the type ##STR3## wherein R', R" and R'" are saturated alkyl groups possessing from 1 to 4 carbon atoms are described for the same use in French patent application No. 77 12357 (published as U.S. Pat. No. 2,388,874) and of which applicants are also assignees.